A connection-free assembled narrow steel box composite beam bridge and a construction method thereof

Abstract

The application discloses a connection-free assembled narrow-width steel box composite beam bridge, which comprises UHPC waffle plates, polyurethane cement-based composite layers, narrow-width steel box beams and inter-box cross beams, the narrow-width steel box beams are provided in plurality, and the plurality of narrow-width steel box beams are arranged in parallel, the polyurethane cement-based composite layers are cast on the upper surfaces of the narrow-width steel box beams, the UHPC waffle plates are cast above the polyurethane cement-based composite layers, the UHPC waffle plates are provided in plurality, and two adjacent groups of the UHPC waffle plates are connected through UHPC joints cast on the polyurethane cement-based composite layers, and the inter-box cross beams are fixedly arranged between the two adjacent narrow-width steel box beams, and a construction method thereof is also disclosed. The application relates to the technical field of bridge engineering, and specifically provides a connection-free assembled narrow-width steel box composite beam bridge and a construction method thereof.

Description

Technical Field

[0001] The present invention relates to the technical field of bridge engineering, and in particular to a connector-free assembled narrow steel box composite beam bridge and a construction method thereof. Background Art

[0002] A steel-concrete composite beam bridge is a bridge structure in which connectors connect steel beams and concrete slabs to form an integral structure. This structure leverages the advantages of concrete in bearing high compressive stresses and steel in bearing high shear stresses. Steel-concrete composite beam bridges also feature high load-bearing capacity, light weight, high rigidity, and good ductility, making them the most widely used bridge structure during this period. To enhance the composite beam's torsional resistance, overall stability, and span capacity, a steel box-concrete composite beam is generally used. Conventional steel boxes typically have a chamber width of 2 meters or more, making them large and inconvenient to transport and install.

[0003] At the same time, ordinary steel box-concrete composite beams still have many shortcomings as follows, such as the concrete is prone to cracking at the place where the bolt connectors are used, and the overall performance of the steel-concrete composite beam is poor, which is not conducive to the durability of the structure. Currently, the commonly used shear connectors are bolt connectors, PBL connectors, and steel connectors. The amount of welding of bolt connectors is large, and their fatigue resistance is poor, and their pull-out strength is also very weak. PBL connectors have the problem of difficulty in positioning and arranging the through steel bars. The pull-out resistance of steel connectors is weak, and it is easy for the steel box beam to peel off from the concrete. The above various connection methods have their advantages, but they also have limitations in construction and mechanical properties. Based on this, it is very necessary to develop a connection method that is convenient to construct, has excellent mechanical properties, reliable connection, and excellent overall performance to replace the commonly used connection methods. Therefore, it is necessary to provide a beam bridge with a more optimized and reasonable structure, good shear resistance, and stronger durability and integrity. Summary of the Invention

[0004] In view of the above situation, in order to remedy the above-mentioned existing defects, the present invention provides a connector-free assembled narrow steel box composite beam bridge and a construction method thereof, which has a simple structure and a high degree of prefabrication and assembly. In particular, in this scheme, a polyurethane cement-based composite layer is used to replace the shear connectors of the traditional connector-free assembled narrow steel box composite beam bridge, thereby enhancing the shear resistance of the composite beam, improving the integrity and durability of the composite beam, reducing on-site workload, and effectively shortening the construction period.

[0005] The present invention provides the following technical solutions:

[0006] One object of the present invention is to provide a connector-free assembled narrow steel box composite beam bridge, comprising UHPC waffle plates, a polyurethane cement-based composite layer, a narrow steel box beam, and a cross beam between the boxes. The narrow steel box beams are provided in plurality and arranged in parallel. The polyurethane cement-based composite layer is cast on the upper surface of the narrow steel box beam, the UHPC waffle plates are cast above the polyurethane cement-based composite layer, the UHPC waffle plates are provided in multiple groups, and two adjacent groups of the UHPC waffle plates are connected by casting a UHPC joint on the polyurethane cement-based composite layer. The cross beam between the boxes is fixedly arranged between two adjacent narrow steel box beams.

[0007] In this solution, the raw materials of the polyurethane cement-based composite layer include polyisocyanate, polyether polyol, cement, admixture and reaction catalyst, wherein the polyisocyanate is WANNATE PM-200, which is a mixture of isocyanate with a certain capacity and high functionality and diphenylmethane diisocyanate; the polyether polyol is WANNOL-P-191212, which is a low molecular weight polyether; the cement is Shanshui PO 425 Portland cement; AS-GS, a homemade micron-grade aluminum silicate powder admixture, is used as an admixture; the reaction catalyst is CPCAT-PUS, an environmentally friendly catalyst produced by Guangzhou Yourun Chemical Company; the polyurethane cement-based composite layer is prepared by the following method: first, polyether polyol and admixture are mixed evenly, then cement is added and stirred for 3-5 minutes, polyisocyanate is added and rapidly stirred for 1-2 minutes after all cement particles are mixed evenly, and finally an appropriate amount of reaction catalyst is added; when the mixture is fully and evenly mixed and a small amount of heat is released, the polyurethane cement-based composite layer is cast and constructed, and demolding can be carried out 24 hours after casting, and curing can be completed by 7 days after demolding; the polyurethane cement-based composite layer is prepared in an environment with a temperature of 16-20°C and a humidity below 50%.

[0008] Furthermore, the narrow steel box girder includes an upper flange steel plate of the narrow steel box girder, a lower flange steel plate of the narrow steel box girder and two corrugated steel webs, the two corrugated steel webs are placed on both sides between the upper flange steel plate and the lower flange steel plate, the upper end of the corrugated steel web is welded to the upper flange steel plate of the narrow steel box girder, and the lower end of the corrugated steel web is welded to the lower flange steel plate of the narrow steel box girder, and a plurality of cross diaphragms are welded equidistantly between the lower flange steel plate of the narrow steel box girder and the upper flange steel plate of the narrow steel box girder, a circular hole is opened in the center of the cross diaphragm, and a plurality of the upper flange steel plates of the narrow steel box girder are provided, and a notch is opened on the top wall of the upper flange steel plate of the narrow steel box girder, and a polyurethane cement-based composite layer is cast at the top surface joints of the two adjacent upper flange steel plates of the narrow steel box girder and the notch positions of the upper flange steel plates of the narrow steel box girder.

[0009] Furthermore, the cross beam between boxes includes a cross beam butt plate, a cross beam body and a transverse connector, the cross beam butt plate is welded to the outside of the corrugated steel web of the narrow steel box beam, the cross beam butt plate includes a cross beam butt plate top plate, a cross beam butt plate web plate and a cross beam butt plate bottom plate, the cross beam butt plate web plate is vertically welded between the cross beam butt plate top plate and the cross beam butt plate bottom plate, the cross beam body includes a cross beam top plate, a cross beam web plate and a cross beam bottom plate, the cross beam web plate is vertically welded between the cross beam top plate and the cross beam bottom plate, the cross beam butt plate top plate and the cross beam butt plate bottom plate The ends of the crossbeam and the two ends of the crossbeam top plate and the crossbeam bottom plate are provided with a plurality of through holes. The cross connecting piece is an I-shaped component. The cross connecting piece is provided with an I-shaped limiting hole. The top and bottom surfaces of the cross connecting piece are provided with a plurality of limiting circular holes. The positions of the limiting circular holes correspond to the positions of the through holes one by one. The end heads of the cross beam body and the cross beam docking plate are matched and installed with the I-shaped limiting holes of the cross connecting piece. The cross beam docking plate and the cross beam body are connected to the cross connecting piece through studs, and the studs are provided through the limiting circular holes and the through holes.

[0010] Furthermore, the UHPC waffle board includes a UHPC panel, UHPC longitudinal ribs and UHPC transverse ribs, the UHPC longitudinal ribs and UHPC transverse ribs are arranged below the UHPC panel, the UHPC longitudinal ribs and UHPC transverse ribs are orthogonal, the UHPC longitudinal ribs and UHPC transverse ribs are arranged at the same height, and two layers of upper and lower steel mesh are arranged in the UHPC waffle board, and the upper and lower layers of the steel mesh are located between the UHPC longitudinal ribs and UHPC transverse ribs.

[0011] Furthermore, the UHPC waffle board is a prefabricated board, and notches are reserved on the UHPC waffle board. Protruding steel bars are provided at the connection positions of adjacent UHPC waffle boards. The protruding steel bars are fixed by polyurethane cement that is interlaced and surrounded by each other. The joints of adjacent UHPC waffle boards are assembled into a whole by pouring UHPC on the polyurethane cement-based composite layer.

[0012] Furthermore, the polyurethane cement-based composite layer has a thickness of 4 cm to 6 cm.

[0013] Furthermore, multiple groups of the inter-box cross beams are arranged along the length direction of the narrow steel box beam, and the spacing between two adjacent groups of the inter-box cross beams is 10m-20m.

[0014] Furthermore, the distance between two adjacent transverse partitions is 5m-10m.

[0015] Furthermore, the distance between the two corrugated steel webs is 1.0m-1.2m.

[0016] Another object of the present invention is to provide a construction method for an assembled narrow steel box composite beam, which is characterized by comprising the following steps:

[0017] Step (1): The narrow steel box girder segments are manufactured in the factory according to the dimensions on the drawings. The length of the narrow steel box girder segments is adjusted according to factors such as transportation and hoisting capacity. The shape of the narrow steel box girder should be accurately processed during manufacturing to ensure reliable welding, and the crossbeam body, crossbeam butt plates and transverse connectors should be manufactured;

[0018] Step (2): The factory accurately manufactures the UHPC waffle plate according to the drawing dimensions and pays attention to the reserved notches;

[0019] Step (3): transport the narrow steel box girder to the construction site using vehicles according to the specific conditions of the bridge location;

[0020] Step (4): After the narrow steel box girder segments are transported to the designed location, a bracket is set up under the main beam of the bridge. After ensuring the reliability of the bracket, the narrow steel box girder segments are hoisted, and all the narrow steel box girder segments are assembled into a complete narrow steel box girder. Polyurethane cement is prepared and poured into the joints and notches on the top surface of the flange steel plate of the narrow steel box girder to make it self-leveling. The crossbeam body and the crossbeam butt plate are connected with transverse connectors;

[0021] Step (5): 24 hours after the pouring is completed, the polyurethane cement-based composite layer is demoulded, and after demoulding, it is cured for 7 days, all UHPC waffle boards are hoisted, and UHPC in the wet joints and grooves is poured;

[0022] Step (6): After the UHPC concrete in the wet joints and notches reaches the design strength, the installation of ancillary facilities such as the bridge deck pavement is completed.

[0023] The beneficial effects achieved by the present invention using the above structure are as follows: The connector-free assembled narrow steel box composite beam bridge and its construction method proposed in the present invention have the following advantages over traditional connector-free assembled narrow steel box composite beam bridges:

[0024] 1. The present invention uses a polyurethane cement-based composite layer to replace traditional shear connectors. Polyurethane cement has the characteristics of light weight, high strength, high toughness, and corrosion resistance. On-site, only the polyurethane cement-based composite layer needs to be cast, without the need for extensive welding and bolting. This avoids the fatigue resistance and pull-out resistance limitations of conventional shear connectors, ensures the accuracy of the connection, reduces on-site workload, shortens the construction period, and improves the connection effect between concrete and steel box beams. There is no peeling between the concrete and steel box beams, ensuring the effective transmission of shear force, enhancing the shear resistance of the composite beam, and improving the structural integrity and durability. It has good promotion and application value.

[0025] 2. The present invention has a simple structure and a high degree of prefabrication and assembly. The narrow steel box girders, UHPC waffle panels, and inter-box beams are all factory-made. On-site construction requires only the pouring of the polyurethane cement-based composite layer and the UHPC cast-in-place portion, as well as the matching installation of the inter-box beams. This simplifies the construction process, shortens the construction period, and avoids excessive impact on the surrounding environment. The UHPC waffle panels have a relatively simple structure, save on UHPC material, are lightweight, offer better economic efficiency, and are easy to construct. Prefabrication allows for scalable and standardized production, which can improve the construction quality of the waffle panel structure and accelerate construction speed.

[0026] 3. The narrow steel box girder used in this invention can reduce the number of longitudinal and transverse stiffeners and diaphragms in the composite beam. The corrugated steel web replaces the flat steel web, which greatly improves the shear strength and stability of the web. The narrow steel box girder can save steel, reduce costs, speed up construction, save labor costs and related measures, and reduce the cost of subsequent painting and maintenance, resulting in significant economic benefits.

[0027] 4. The present invention adopts a transverse connector to connect the beam body and the beam docking plate, so as to realize convenient installation and stable connection of the beam body and the beam docking plate, thereby improving stability; the bolt connection is adopted to reduce the on-site workload and facilitate later maintenance and replacement. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0029] Figure 1 It is an overall schematic diagram of the present invention;

[0030] Figure 2 This is a schematic diagram of the decomposition of a single narrow steel box girder structure of the present invention;

[0031] Figure 3 This is a schematic diagram of a three-dimensional structure of multiple narrow steel box girders of the present invention;

[0032] Figure 4 This is a schematic diagram of the cross beam structure between boxes of the present invention;

[0033] Figure 5 This is a schematic diagram of the structure of the transverse connector of the present invention;

[0034] Figure 6 This is a schematic diagram of the crossbeam body structure of the present invention;

[0035] Figure 7 This is a schematic diagram of the UHPC waffle plate structure of the present invention;

[0036] Figure 8This is a schematic diagram of the cross-section structure of a partial structure of the UHPC waffle plate of the present invention.

[0037] Among them, 1. UHPC waffle plate, 2. narrow steel box girder, 3. narrow steel box girder upper flange steel plate, 4. narrow steel box girder lower flange steel plate, 5. corrugated steel web, 6. diaphragm, 7. polyurethane cement-based composite layer, 8. inter-box beam, 9. beam butt plate, 10. beam body, 11. transverse connector, 12. through hole, 13. limiting circular hole, 14. stud, 15. UHPC joint, 16. UHPC panel, 17. UHPC longitudinal rib, 18. UHPC transverse rib, 19. steel mesh. DETAILED DESCRIPTION

[0038] The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments; based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0039] Example

[0040] Reference Figure 1 and Figure 3In this embodiment, a connector-free assembled narrow steel box composite beam bridge includes a UHPC waffle plate 1, a polyurethane cement-based composite layer 7, a narrow steel box beam 2 and a box cross beam 8. The narrow steel box beam 2 is provided with a plurality of narrow steel box beams 2, and the plurality of narrow steel box beams 2 are arranged in parallel. The polyurethane cement-based composite layer 7 is cast on the upper surface of the narrow steel box beam 2, and the UHPC waffle plate 1 is cast above the polyurethane cement-based composite layer 7. The UHPC waffle plate 1 is provided with a plurality of groups, and two adjacent groups of the UHPC waffle plates 1 are connected by the polyurethane The UHPC joint 15 is poured on the cement-based composite layer 7 for connection. The box cross beam 8 is fixedly arranged between two adjacent narrow steel box beams 2. The thickness of the polyurethane cement-based composite layer 7 is 4cm-6cm. The box cross beam 8 is provided in multiple groups along the length direction of the narrow steel box beam 2, and the spacing between two adjacent groups of the box cross beam 8 is 10m-20m. The raw materials of the polyurethane cement-based composite layer 7 include polyisocyanate, polyether polyol, cement, admixture and reaction catalyst, wherein the polyisocyanate is WANNATE PM-200 is a mixture of isocyanate and diphenylmethane diisocyanate containing a certain amount of high functionality; WANNOL-P-191212 is a low molecular weight polyether polyol; Shanshui PO 425 silicate cement is used as cement; AS-GS is a homemade micron-grade aluminum silicate powder admixture as an admixture; and the reaction catalyst is the environmentally friendly catalyst CPCAT-PUS produced by Guangzhou Yourun Chemical Company. The polyurethane cement-based composite layer 7 is prepared by first mixing the polyether polyol and the admixture evenly, then adding the cement and stirring for 3-5 minutes. After all the cement particles are evenly mixed, the polyisocyanate is added and stirred rapidly for 1-2 minutes. Finally, an appropriate amount of the reaction catalyst is added. When the mixture is fully and evenly mixed and a small amount of heat is released, the polyurethane cement-based composite layer 7 is cast. The layer can be demoulded 24 hours after casting and cured for 7 days after demoulding. The polyurethane cement-based composite layer 7 is prepared in an environment with a temperature of 16-20°C and a humidity below 50%.

[0041] In this solution, a polyurethane cement-based composite layer is used to replace traditional shear connectors. Polyurethane cement has the characteristics of light weight, high strength, high toughness and corrosion resistance. Only the pouring of the polyurethane cement-based composite layer needs to be completed on site, without the need for a large amount of welding and bolting. This avoids the limitations of fatigue resistance and tensile strength of conventional shear connectors, ensures the accuracy of the connection, reduces on-site workload, shortens the construction period, and increases the connection effect between concrete and steel box beams. There will be no peeling between concrete and steel box beams, ensuring the effective transmission of shear force, enhancing the shear resistance of the composite beam, and improving the structural integrity and durability.

[0042] Specifically, refer to Figure 2 and Figure 3In this embodiment, the narrow steel box girder 2 includes a narrow steel box girder upper flange steel plate 3, a narrow steel box girder lower flange steel plate 4 and two corrugated steel webs 5. The two corrugated steel webs 5 are placed on both sides between the upper flange steel plate 3 and the lower flange steel plate 4. The distance between the two corrugated steel webs 5 is 1.0m-1.2m; the upper end of the corrugated steel web 5 is welded to the narrow steel box girder upper flange steel plate 3, and the lower end of the corrugated steel web 5 is welded to the narrow steel box girder lower flange steel plate 4. A plurality of transverse partitions 6 are welded at equal intervals between the lower flange steel plate 4 of the steel box girder and the upper flange steel plate 3 of the narrow steel box girder, and the distance between two adjacent transverse partitions 6 is 5m-10m; a circular hole is opened in the center of the transverse partition 6, and the narrow steel box girder upper flange steel plate 3 is provided with a plurality of transverse partitions 6, and a notch is opened on the top wall of the narrow steel box girder upper flange steel plate 3, and a polyurethane cement-based composite layer 7 is cast at the top surface joints of the two adjacent narrow steel box girder upper flange steel plates 3 and the notch position of the narrow steel box girder upper flange steel plate 3.

[0043] Specifically, refer to Figure 4 、 Figure 5 and Figure 6 The box beam 8 includes a beam butt plate 9, a beam body 10 and a transverse connector 11. The beam butt plate 9 is welded to the outside of the narrow steel box beam corrugated steel web 5. The beam butt plate 9 includes a beam butt plate top plate, a beam butt plate web plate and a beam butt plate bottom plate. The beam butt plate web plate is vertically welded between the beam butt plate top plate and the beam butt plate bottom plate. The beam body 10 includes a beam top plate, a beam web plate and a beam bottom plate. The beam web plate is vertically welded between the beam top plate and the beam bottom plate. The ends of the beam butt plate top plate and the beam butt plate bottom plate, as well as the beam top plate and the beam There are several through holes 12 at both ends of the bottom plate. The transverse connector 11 is an I-shaped component. The transverse connector 11 is provided with an I-shaped limiting hole. The top and bottom surfaces of the transverse connector 11 are provided with several limiting circular holes 13. The positions of the limiting circular holes 13 correspond one-to-one to the positions of the through holes 12. The end heads of the beam body 10 and the beam docking plate 9 are matched and installed with the I-shaped limiting holes of the transverse connector 11. The beam docking plate 9 and the beam body 10 are connected to the transverse connector 11 through studs 14. The studs 14 are arranged through the limiting circular holes 13 and the through holes 12.

[0044] Specifically, refer to Figure 7 and Figure 8The UHPC waffle plate 1 includes a UHPC panel 16, UHPC longitudinal ribs 17 and UHPC transverse ribs 18, wherein the UHPC longitudinal ribs and UHPC transverse ribs are arranged below the UHPC panel 16, and the UHPC longitudinal ribs 17 and UHPC transverse ribs 18 are orthogonal to each other and are arranged at the same height. Two layers of upper and lower steel mesh 19 are arranged in the UHPC waffle plate 1, and the upper and lower layers of the steel mesh 19 are located between the UHPC longitudinal ribs 17 and the UHPC transverse ribs 18; the UHPC waffle plate 1 is a prefabricated plate, and notches are reserved on the UHPC waffle plate 1. Protruding steel bars are provided at the connection positions of adjacent UHPC waffle plates 1, and the protruding steel bars are fixed by interlacing and surrounding polyurethane cement. The joints of adjacent UHPC waffle plates 1 are assembled into a whole by pouring UHPC on the polyurethane cement-based composite layer 7.

[0045] Another object of the present invention is to provide a construction method for an assembled narrow steel box composite beam, which is characterized by comprising the following steps:

[0046] Step (1): The narrow steel box girder segments are manufactured in the factory according to the dimensions on the drawings. The length of the narrow steel box girder segments is adjusted according to factors such as transportation and hoisting capacity. The shape of the narrow steel box girder 2 should be accurately processed during manufacturing to ensure reliable welding, and the crossbeam body 10, crossbeam butt plate 9 and transverse connector 11 should be manufactured.

[0047] Step (2): The factory accurately manufactures the UHPC waffle plate 1 according to the drawing dimensions and pays attention to the reserved notches;

[0048] Step (3): transport the narrow steel box girder 2 to the construction site using a vehicle according to the specific conditions of the bridge location;

[0049] Step (4): After the narrow steel box girder segments are transported to the designed location, a bracket is set up under the main beam of the bridge. After ensuring the reliability of the bracket, the narrow steel box girder segments are hoisted, and all the narrow steel box girder segments are assembled into a complete narrow steel box girder 2. Polyurethane cement is prepared and poured into the top surface joints and notches of the flange steel plate 3 of the narrow steel box girder to make it self-leveling. The crossbeam body 10 and the crossbeam butt plate 9 are connected with a transverse connector 11;

[0050] Step (5): 24 hours after the pouring is completed, the polyurethane cement-based composite layer is demoulded, and after demoulding, it is cured for 7 days, all UHPC waffle plates 1 are hoisted, and UHPC in the wet joints and grooves is poured;

[0051] Step (6): After the UHPC concrete in the wet joints and notches reaches the design strength, the installation of ancillary facilities such as the bridge deck pavement is completed.

[0052] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, material, or apparatus that includes a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, material, or apparatus.

[0053] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A connector-free assembled narrow steel box composite beam bridge, characterized in that: The invention comprises a UHPC waffle plate (1), a polyurethane cement-based composite layer (7), a narrow steel box beam (2) and an inter-box cross beam (8), wherein a plurality of narrow steel box beams (2) are provided, and the plurality of narrow steel box beams (2) are arranged in parallel, the polyurethane cement-based composite layer (7) is cast on the upper surface of the narrow steel box beam (2), the UHPC waffle plate (1) is cast above the polyurethane cement-based composite layer (7), the UHPC waffle plate (1) is provided in a plurality of groups, two adjacent groups of the UHPC waffle plates (1) are connected by casting a UHPC joint (15) on the polyurethane cement-based composite layer (7), and the inter-box cross beam (8) is fixedly arranged between two adjacent narrow steel box beams (2).

2. The connector-free assembled narrow steel box composite beam bridge according to claim 1, characterized in that: The narrow steel box girder (2) comprises an upper flange steel plate (3) of the narrow steel box girder, a lower flange steel plate (4) of the narrow steel box girder and two corrugated steel webs (5), wherein the two corrugated steel webs (5) are placed on both sides between the upper flange steel plate (3) and the lower flange steel plate (4), wherein the upper ends of the corrugated steel webs (5) are welded to the upper flange steel plate (3) of the narrow steel box girder, and the lower ends of the corrugated steel webs (5) are welded to the lower flange steel plate (4) of the narrow steel box girder. A plurality of transverse diaphragms (6) are welded at equal intervals between the lower flange steel plate (4) and the narrow steel box girder upper flange steel plate (3), wherein a circular hole is opened in the center of the transverse diaphragm (6), the narrow steel box girder upper flange steel plate (3) is provided with a plurality of transverse diaphragms, a notch is opened on the top wall of the narrow steel box girder upper flange steel plate (3), and a polyurethane cement-based composite layer (7) is cast at the top surface joints of two adjacent narrow steel box girder upper flange steel plates (3) and the notch positions of the narrow steel box girder upper flange steel plates (3).

3. The connector-free assembled narrow steel box composite beam bridge according to claim 2, characterized in that: The inter-box cross beam (8) includes a cross beam butt plate (9), a cross beam body (10) and a transverse connector (11), the cross beam butt plate (9) is welded to the outside of the narrow steel box beam corrugated steel web (5), the cross beam butt plate (9) includes a cross beam butt plate top plate, a cross beam butt plate web plate and a cross beam butt plate bottom plate, the cross beam butt plate web plate is vertically welded between the cross beam butt plate top plate and the cross beam butt plate bottom plate, the cross beam body (10) includes a cross beam top plate, a cross beam web plate and a cross beam bottom plate, the cross beam web plate is vertically welded between the cross beam top plate and the cross beam bottom plate, the ends of the cross beam butt plate top plate and the cross beam butt plate bottom plate, as well as the two ends of the cross beam top plate and the cross beam bottom plate are provided with The invention relates to a plurality of through holes (12), wherein the transverse connecting member (11) is an I-shaped member, and an I-shaped limiting hole is provided on the transverse connecting member (11). The top surface and the bottom surface of the transverse connecting member (11) are provided with a plurality of limiting circular holes (13), and the positions of the limiting circular holes (13) correspond to the positions of the through holes (12) in a one-to-one manner. The ends of the crossbeam body (10) and the crossbeam docking plate (9) are matched and installed with the I-shaped limiting holes of the transverse connecting member (11), and the crossbeam docking plate (9) and the crossbeam body (10) are connected to the transverse connecting member (11) through studs (14), and the studs (14) are provided through the limiting circular holes (13) and the through holes (12).

4. The connector-free assembled narrow steel box composite beam bridge according to claim 3, characterized in that: The UHPC waffle plate (1) comprises a UHPC panel (16), UHPC longitudinal ribs (17) and UHPC transverse ribs (18), wherein the UHPC longitudinal ribs and the UHPC transverse ribs are arranged below the UHPC panel (16), the UHPC longitudinal ribs (17) and the UHPC transverse ribs (18) are orthogonal, and the UHPC longitudinal ribs (17) and the UHPC transverse ribs (18) are arranged at the same height, and upper and lower layers of steel mesh (19) are arranged in the UHPC waffle plate (1), and the upper and lower layers of the steel mesh (19) are located between the UHPC longitudinal ribs (17) and the UHPC transverse ribs (18).

5. The connector-free assembled narrow steel box composite beam bridge according to claim 4, characterized in that: The UHPC waffle plate (1) is a prefabricated plate. Notches are reserved on the UHPC waffle plate (1). Protruding steel bars are provided at the positions where adjacent UHPC waffle plates (1) are connected. The protruding steel bars are fixed by polyurethane cement that intersects and surrounds each other. The joints of adjacent UHPC waffle plates (1) are assembled into a whole by pouring UHPC on the polyurethane cement-based composite layer (7).

6. The connector-free assembled narrow steel box composite beam bridge according to claim 3, characterized in that: The polyurethane cement-based composite layer (7) has a thickness of 4 cm to 6 cm.

7. The connector-free assembled narrow steel box composite beam bridge according to claim 3, characterized in that: Multiple groups of the inter-box cross beams (8) are arranged along the length direction of the narrow steel box beam (2), and the spacing between two adjacent groups of the inter-box cross beams (8) is 10m-20m.

8. The connector-free assembled narrow steel box composite beam bridge according to claim 3, characterized in that: The distance between two adjacent transverse partitions (6) is 5m-10m.

9. The connector-free assembled narrow steel box composite beam bridge according to claim 3, characterized in that: The distance between the two corrugated steel webs (5) is 1.0m-1.2m.

10. The construction method of a connector-free assembled narrow steel box composite beam bridge according to any one of claims 3 to 9, characterized in that: The specific steps include: Step (1): The narrow steel box girder segments are manufactured in the factory according to the dimensions on the drawings. The length of the narrow steel box girder segments is adjusted according to factors including transportation and hoisting capacity. The shape of the narrow steel box girder (2) should be accurately processed during manufacturing to ensure reliable welding. The crossbeam body (10), crossbeam butt plate (9) and transverse connector (11) are also manufactured. Step (2): The factory accurately manufactures the UHPC waffle plate (1) according to the drawing dimensions and pays attention to the reserved notches; Step (3): transporting the narrow steel box girder (2) to the construction site using a vehicle according to the specific conditions of the bridge location; Step (4): After the narrow steel box girder segments are transported to the designed location, a bracket is set up under the main beam of the bridge. After ensuring the reliability of the bracket, the narrow steel box girder segments are hoisted, and all the narrow steel box girder segments are assembled into a complete narrow steel box girder (2). Polyurethane cement is prepared and poured into the top surface joints and notches of the flange steel plate (3) of the narrow steel box girder to make it self-leveling. The crossbeam body (10) and the crossbeam butt plate (9) are connected with a transverse connector (11); Step (5): 24 hours after the pouring is completed, the polyurethane cement-based composite layer is demoulded, and after demoulding, it is cured for 7 days, all UHPC waffle boards (1) are hoisted, and UHPC in the wet joints and grooves is poured; Step (6): After the UHPC concrete in the wet joints and notches reaches the design strength, the installation of ancillary facilities including the bridge deck pavement is completed.

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